This invention relates to thickeners for liquid suspensions and pulps and in particular to recycling of overflow liquor in thickeners.
In thickening certain pulps, it is sometimes necessary to first dilute the pulp in order to enable flocculation to take place when a polymer flocculant is added. This is usually achieved in thickeners by recycling some of the dilute liquid (known as "liquor") overflow from the top of the thickener tank back to the feedwell in order to dilute the inflowing pulp.
In the past, in order to recycle the overflow liquor it has been necessary to install a system of pumps, fluid lines and valves. This involves significant capital costs, and gives rise to a further problem of controlling the recycling process, which has hitherto been controlled manually.